The invention discloses an aluminum alloy vacuum electron beam welding method. The method includes: press-fitting welding workpieces and placing the workpieces in a vacuum chamber; preheating with 4-8mA electron beam current, under the scanning frequency of 80-200Hz, X-axial and Y-axial scanning amplitude of 200-300, and welding speed of 450-60mm/s; positioning and pre-connecting with 10-15Ma butt beam current, under the scanning frequency of 80-200Hz, X-axial and Y-axial scanning amplitude of 200-300 and welding speed of 450-600mm/s; performing penetration welding with 10-15mA electron beam current, under the scanning frequency of 80-200Hz, X-axial and Y-axial scanning amplitude of 200-300Hz and welding speed of 450-600mm/s; finally trimming welds. The method is simple, weld quality is good, few pores occur, the welds are attractive, and little deformation of the workpieces occurs.